Detailed information concerning the prenatal neurogenesis of some neurons and fibers of the human cerebellum is lacking. I propose to carry out prenatal developmental studies of various neurons and fibers of the human cerebellum and to analyze their developmental interrelationships. I will use the rapid Golgi method in these developmental studies. The principal objectives to pursue are the following. (1) Neurogenesis of the mossy fibers, and of its multiple neuronal connections. This study will also try to determine if the human climbing and mossy fibers are indistinguishable, early in their development and share temporarily the same neuronal targets. (2) Neurogenesis of the Golgi cell. This study will try to determine if there are more than one type of Golgi cell in the human cerebellum, or, if they have more than one maturation spur. (3) Neurogenesis of the Lugaro and Interstitial cells. This study will try to determine if these neurons are structurally and functionally part of the basic Climbing-Purkinje System. (4) Neurogenesis of the abnormal cerebellum of four infants with bilateral renal agenesis (Potter's syndrome). Preliminary observations have disclosed peculiar dendritic and axonic anomalies in the structure of developing Purkinje cells not previously described. (5) Progressive reconstruction of 'maps' of the fibrillar neuronal organization of the human cerebellum at different prenatal (25, 30, 35, and 40 week gestation) and early postnatal (1 and 5 year of age) developmental stages, to be used in future studies of normal and abnormal cerebellar development. (6) Continue by Golgi studies of the human cerebral cortex which started many years ago.